Analysis of geometric and thermal errors of linear encoder for real-time compensation

Abstract

Thermal errors that cause temperature deformations is one of the main factors that influence the accuracy of precision machines. Displacement measuring systems are used in robotics, precision machine tools and other technological equipment, where exist abundant heat sources. The accuracy of linear encoder is affected by both: thermal sources and the changing external ambient temperature. Therefore, thermo-elastic deformations occurring due to the changes in the ambient temperature is an important factor that should be estimated in the process of machine operation. This article presents a study on the thermal errors of optical linear encoder. Compensation of thermal errors is considered a more convenient, effective and economical way in comparison to the ways of thermal error handling and reduction. On the basis of analytic calculations, digital FEM analysis and experimental research, the models of thermal errors that are used for the real-time compensation are determined. The methodology of thermal error compensation, which could be easily realized in a linear encoder itself is presented in the article.